Endless retainer of guide device and fabrication method thereof

ABSTRACT

An endless retainer of a guide device including a number of rolling bodies arranged at predetermined intervals for rolling at an inside of an infinite track formed in the guide device, a flexible resin connector having interposing portions interposed among the respective rolling bodies and connecting portions for connecting the respective interposing portions for holding the number of rolling bodies in an aligned state and rotatably, and the resin connector is molded by an injection molding with the rolling bodies as cores by using a resin having a dimension change rate before and after an oil absorbing or a water absorbing treatment larger than a mold shrinkage rate and is provided with clearances between the resin connector and the rolling bodies formed by the oil absorbing or the water absorbing treatment whereby handling thereof is facilitated without detaching the rolling bodies, automation of integrating the endless retainer to the guide device can be carried out and extremely smooth rotatability can be provided to the rolling bodies with certainty.

FIELD OF THE INVENTION

The present invention relates to an endless retainer in a guide deviceof, for example, a linear guide device, a curved guide device, apivoting bearing or the like for infinite sliding, which is insertedinto an infinite track thereof and which supports relative linearmovement or rotational movement between a pair of bearing races formingthe infinite track, and its fabrication method.

DESCRIPTION OF RELATED ART

According to various guide devices having bearings, linear movement orrotational movement between bearing races can be carried out byutilizing rolling movement of rolling bodies comprising balls or rollerssandwiched between a pair of the bearing races. It is general tointegrate a number of the rolling bodies between the bearing races byholding them by a retainer or a cage made of a metal thin plate orsynthetic resin with purposes of preventing detachment of the rollingbodies when the pair of bearing races are separated from each other,achieving reduction in frictional resistance by avoiding contact amongthe respective rolling bodies, obtaining smooth movement by aligning therespective rolling bodies at predetermined positions and so on.

However, according to a conventional guide device using a retainer, theguide device is integrated by integrating the retainer to a side ofeither of the bearing races, integrating the rolling bodies to a formedrolling path of the rolling bodies and successively integrating other ofthe bearing races. Particularly when the guide device includes aninfinite track of the rolling bodies, skill is required in the operationof integrating the guide device using the retainer and its automation isdifficult.

Further, according to a conventional guide device using a cage, the cageis provided with a number of pockets and the respective rolling bodiesare rotatably held in the pockets and accordingly, there is provided anadvantage where the operation of integrating a number of the rollingbodies to the guide device is facilitated. However, there poses otherproblem in which a number of the rolling bodies need to be integrated inthe respective pockets of the cage and held thereby such that therolling bodies are not detached and enormous time and labor is requiredin fabricating the cage per se.

Hence, in order to resolve such problems, there have been proposed aball retainer or a ball cage in a chain-like shape which is fabricatedby injection molding of resin where balls are arranged as cores at asubstantially flat face in a mold and forms a predetermined shape bybeing folded or bent in using it (Japanese Examined Patent PublicationNo. JP-B-6-56181, Japanese Unexamined Patent Publication No.JP-A-5-52217, Japanese Unexamined Patent Publication No. JP-A-5-126149,Japanese Unexamined Patent Publication No. JP-A-5-196036 and JapaneseUnexamined Patent Publication No. JP-A-5-196037).

However, according to the ball retainer or the ball cage in a chain-likeshape, rotatability is provided to the balls which have been cast ascores in the resin by utilizing a property of the resin that it iscontracted after the injection molding. Accordingly, there are caseswhere an extremely long period of time is required for providing therotatability to the balls, it is difficult to provide the smoothrotatability and the rotatability cannot be provided to the ballsdepending on the kind of resin.

SUMMARY OF THE INVENTION

The present invention has solved difficulty in handling a conventionalretainer or a cage for rolling bodies and resolved the problem of theball cage or the ball retainer in a chain-like shape which haspreviously been proposed and it is an object of the present invention toprovide an endless retainer not only having advantages where theretainer can be fabricated extremely easily, handling thereof isextremely facilitated without detaching rolling bodies and an automationin integrating the retainer to a guide device can be carried out, butbeing capable of extremely smooth rotatability to the rolling bodieswith certainly, and its fabrication method.

Hence, according to an aspect of the present invention, there isprovided an endless retainer of a guide device, the endless retainercomprising a number of rolling bodies arranged at predeterminedintervals for rolling at an inside of an infinite track formed in theguide device, a flexible resin connector having interposing portionsinterposed among the respective rolling bodies and connecting portionsfor connecting the respective interposing portions for holding thenumber of rolling bodies in an aligned state and rotatably, and theresin connector is molded by an injection molding with the rollingbodies as cores by using a resin having a dimension change rate beforeand after an oil absorbing or a water absorbing treatment larger than amold shrinkage rate and is provided with clearances between the resinconnector and the rolling bodies formed by the oil absorbing or thewater absorbing treatment.

Further, according to another aspect of the present invention, there isprovided a method of fabricating an endless retainer for molding theresin connector holding the number of rolling bodies by an injectionmolding with the number of rolling bodies as cores by using a resinhaving a dimension change rate before and after an oil absorbing or awater absorbing treatment larger than a mold shrinkage rate, and formingclearances between the resin connector and the respective rolling bodiesfor rotating the rolling bodies by subjecting the resin connector to theoil absorbing or the water absorbing treatment after having been removedfrom a mold.

According to the present invention, resin used for molding the resinconnector must be a resin having the dimension change rate before andafter the oil absorbing or the water absorbing treatment larger than themold shrinkage rate and a difference between the dimension change ratebefore and after the oil absorbing or the water absorbing treatment andthe mold shrinkage rate preferably falls in a range of 0.1 through 2.0%,more preferably, 0.5 through 1.5%. When the difference between thedimension change rate before and after the oil absorbing or the waterabsorbing treatment and the mold shrinkage rate falls in a range of 0.1through 2.0%, excellent rotatability of the rolling bodies can beprovided by forming the clearances between the resin connector and therolling bodies with certainty by the oil absorbing or the waterabsorbing treatment. Further, when the dimension change rate before andafter the oil absorbing or the water absorbing treatment becomesexcessively large by exceeding the magnitude of the mold shrinkage rate,there is a concern where the rolling bodies are detached from the resinconnector after the oil absorbing or the water absorbing treatment,however, according to experiments by the inventors, the difference isthe utmost of about 2 through 3% and there is no concern of detachingthe rolling bodies from the resin connector with such a degree of themagnitude.

Here, the dimension change rate before and after the oil absorbing orthe water absorbing treatment is a percentage of a value (elongationamount) of a length (length after treatment) of the resin connector(endless retainer) after the oil absorbing or the water absorbingtreatment subtracted by a length (length before treatment) of the resinconnector (endless retainer) before the oil absorbing or the waterabsorbing treatment as compared with the length (length beforetreatment) of the resin connector (endless retainer) before the oilabsorbing or the water absorbing treatment and the mold shrinkage rateis a value calculated by the following equation in accordance with JISK6911,5.7.

Mold shrinkage rate={(mold dimension-molded product dimension)÷molddimension}×100

Further, in respect of the resin used for molding the resin connectoraccording to the present invention, it is necessary that the moldedresin connector can smoothly be moved along with the rolling bodies inan infinite track of the rolling bodies formed by bearing races of theguide device and for that purpose, the resin of the resin connectorneeds to have flexibility and Shore hardness of the resin preferablyfalls in a range of 35 through 75, more preferably, 40 through 60.

As the resin preferable in fabricating the resin connector having such aflexibility, for example, there are polyamide-base elastomer such asPebax (commercial name made by Toray Corporation) or the like,polyester-base elastomer such as Hytrel (commercial name made by Torayand DuPont Corporations) or the like, elastomers of polyurethane-baseelastomer, styrene-base elastomer, olefin-base elastomer and the like,soft polyvinyl chloride and so on and elastomers are preferable.Further, among the elastomers, in consideration of properties requiredfor the resin connector, particularly, softness or flexibility, thedimension change rate in absorbing oil or absorbing water, chemicalproof, elongation and the like, polyamide-base or polyester-baseelastomer is more preferable and further, in consideration of a timeperiod whereby the elongation amount reaches a saturated state in theoil absorbing or the water absorbing treatment, in other words, a timeperiod until a change in dimension is stabilized (dimension stabilizingtime), polyester-base elastomer is preferable.

Further, according to the present invention, a ball or a roller ispointed out as the rolling body used in the guide device and the ball ispreferable in an endless retainer used in a guide device necessitatingsmooth slidability and the roller is preferable for an endless retainerused in a guide device necessitating to apply comparatively heavy load.

In fabricating an endless retainer according to the present invention,resin having the dimension change rate before and after the oilabsorbing or the water absorbing treatment larger than the moldshrinkage rate is used, the resin connector holding the number ofrolling bodies is molded by injection molding with the number of rollingbodies as cores and after removing the resin connector from a mold,clearances for rotating the rolling bodies are formed between the resinconnector and the respective rolling bodies by subjecting the resinconnector to the oil absorbing or the water absorbing treatment.

Here, in respect of injection molding with a number of rolling bodies ascores, so-called insert molding processes such as methods described inJapanese Examined Patent Publication No. JP-B-6-56181, JapaneseUnexamined Patent Publication No. JP-A-5-52217, Japanese UnexaminedPatent Publication No. JP-A-5-126149, Japanese Unexamined PatentPublication No. JP-A-5-196036 and Japanese Unexamined Patent PublicationNo. JP-A-5-196037 mentioned above are applicable.

Further, in respect of the oil absorbing or the water absorbingtreatment for providing rotatability to the respective rolling bodies inthe molded endless retainer, although arbitrary methods of a method ofdipping an endless retainer which has been removed from a mold into oilor water, a method of spraying misty oil or water to an endless retainerwhich has been removed from a mold, a method of making an endlessretainer which has been removed from a mold absorb oil or water underpredetermined heating and pressing by using an autoclave or the like, amethod of leaving an endless retainer which has been removed from a moldunder high humidity, a method of leaving an endless retainer which hasbeen removed from a mold in the atmosphere for a predetermined timeperiod, and the like can be adopted, the preferable method is the methodof dipping an endless retainer which has been removed from a mold intooil or into water and the more preferable method is the method fordipping the endless retainer into oil.

Further, also in respect of treatment conditions of the oil absorbing orthe water absorbing treatment in this case, pertinent conditions can beselected and adopted depending on the method of treatment, the kind ofresin used and the like, for example, according to the method of dippingan endless retainer which has been removed from a mold into oil or intowater, normally, the endless retainer is normally dipped at temperatureof normal temperature through 50° C. for several minutes through severalhours, although the conditions differ also depending on the kind ofresin.

The oil absorbing or the water absorbing treatment is for providingrotatability to a rolling body of a molded endless retainer and althoughwhen the rotatability is provided to the rolling body by the oilabsorbing treatment, the rolling body can be integrated to a guide as itis, when, for example, moisture is adhered to the surface of the endlessretainer after the treatment as in the case where the water absorbingtreatment is carried out by dipping the endless retainer into water, theendless retainer is integrated to the guide device preferably afterremoving the moisture adhered to the surface.

As oil used in the oil absorbing treatment, although liquid lubricant,grease or petrolatum of semi-solid lubricant or the like havinglubricating performance may be used, the oil is preferably liquidlubricant having lubricating performance, for example, lubricant ofmineral oil-base or synthetic oil-base, lubricant of emulsion-base,liquid metal-base, water-base or the like can be pointed out.

Although in the oil absorbing or the water absorbing treatment, anelongation amount of an endless retainer after the treatment as comparedwith that before the treatment, that is, the elongation amount of theresin connector reaches to a saturated state after a constant period oftime, the oil absorbing or the water absorbing treatment is not alwaysnecessary to carry out until the elongation amount reaches the saturatedstate, it is sufficient that the elongation amount of at least 0.1% ormore, preferably, 0.3% or more in respect of the length before thetreatment is shown and free rotatability of respective rolling bodies isprovided to the resin connector.

However, when an endless retainer provided by finishing the oilabsorbing or the water absorbing treatment is used by integrating it toa guide device before reaching the saturated state, the resin connectorof the endless retainer absorbs lubricant used in the guide device andis elongated until it reaches the saturated state and there is a concernof effecting a hazard in the smooth sliding movement of the endlessretainer in the guide device and accordingly, the oil absorbing or thewater absorbing treatment is preferably carried out until the elongationamount of the endless retainer reaches a state near to the saturatedstate before being integrated to the guide device. Accordingly, in sucha point of view, with respect to resin used as the resin connector, inconsideration of the productivity, polyester-base elastomer having acomparatively short time period whereby elongation amount reaches thesaturated state in the oil absorbing treatment (dimension stabilizingtime) is preferable.

Further, according to the endless retainer of the present invention,chamfered guide portions are preferably formed at both distal ends ofthe resin connector by which in moving an infinite track formed bybearing races of the guide device, particularly when the front endportion of the endless retainer moves into a direction change path ofthe infinite track or when it moves out from the direction change path,the endless retainer can be moved by guiding the front end portion bythe chamfered guide portion.

The chamfered guide portions formed at the both distal ends of the resinconnector, are designed by considering a radius of curvature of thedirection change path of the infinite track formed by the bearing racesof the guide device and determining the size of the radius of curvature,the shape and so on. By forming the chamfered guide portions at the bothdistal ends of the resin connector, in the reciprocating movement of theguide device, the endless retainer can smoothly be guided in either ofdirection of progressing and regressing.

Further, although the length of the molded endless retainer isdetermined by considering the length of the infinite track of the guidedevice where it is used, when the guide device is large-sized and thelength of the infinite track is large, the endless retainer may bemolded by dividing it in a plural number of 2, 3 or the like by whichthe size of a mold for molding the endless retainer can be reduced.Further, in that case, it is preferable to form the chamfered guideportions respectively at both distal ends of the resin connector of eachof the endless retainers divided in the plural number.

According to the present invention, in molding the resin connector byinjection molding with the rolling bodies as cores, the resin connectorholding the rolling bodies after having been removed from a mold, isshrunk in accordance with the magnitude of the mold shrinkage rate, bysubjecting the resin connector to the oil absorbing or the waterabsorbing treatment, the resin connector is expanded in accordance withthe magnitude of the dimension change rate before and after the oilabsorbing or the water absorbing treatment and further, the dimensionchange rate before and after the oil absorbing or the water absorbingtreatment is larger than the mold shrinkage rate and accordingly,portions surrounding the rolling bodies expand to exceed lengths atsurroundings of the rolling bodies and as a result, clearances areformed between the rolling bodies and the resin connector with certaintyby which excellent rotatability seems to be provided to the rollingbodies.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plane view showing an endless retainer in a chain-like shapeaccording to an embodiment of the present invention;

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a sectional view taken along a line III--III of FIG. 1;

FIG. 4 is a partially enlarged plane view showing an end portion of theendless retainer of FIG. 1 by enlargement;

FIG. 5 is a graph diagram showing a time-sequential change in anelongation rate when an oil absorbing treatment is carried out inaccordance with Method A;

FIG. 6 is a graph diagram showing a time-sequential change in anelongation rate when an oil absorbing treatment is carried out inaccordance with Method B;

FIG. 7 is a graph diagram showing a time-sequential change of anelongation rate when a water absorbing treatment is carried out inaccordance with Method C;

FIG. 8 is a graph diagram showing a relationship between an elapse timeand the elongation rate after dipping endless retainers in respect oftwo kinds of endless retainers provided in Embodiment 2;

FIG. 9 is a partially sectional side view showing a linear guide devicefor infinite sliding integrated with an endless retainer fabricated bythe invented method (Method B);

FIG. 10 is a partially sectional front view of FIG. 9; and

FIG. 11 is a graph diagram of measuring rolling resistance by using aload cell which has been measured in respect of the linear guide deviceof FIG. 9.

DESCRIPTION OF REFERENCE NUMERAL

E_(R) : endless retainer, 1 or 1a: ball, 2: resin connector, 2a:interposing portion, 2b: connecting portion, 3: chamfered guide portion,4: track rail (one bearing race), 5: sliding base (other bearing race),5a: loaded ball rolling face, 5b: through hole, 6: ball guide member,6a: unloaded ball guide hole, 6b: loaded ball guide groove, 6c:direction change guiding unit, 7: lid, 8: direction change path.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A specific explanation will be given of an endless retainer according tothe present invention and its fabrication method based on embodiments,test examples and application examples shown by attached drawings asfollows.

Embodiment 1

FIG. 1 through FIG. 4 show an endless retainer E_(R) in a chain-likeshape according to the embodiment of the present invention. The endlessretainer E_(R) is constituted by a number of balls 1 made of bearingsteel (SUJ 2) arranged at predetermined intervals and a flexible resinconnector 2 having interposing portions 2a interposed among therespective balls 1 and connecting portions 2b for connecting therespective interposing portions 2a for holding a number of balls 1linearly and rollably.

Further, according to the embodiment, as shown by FIG. 4, at both distalends of the resin connector 2, chamfered guide portions 3 each having asection substantially in a circle concentric to the balls 1a, are formedat distal end portions surrounding the balls 1a disposed at the distalends.

The endless retainer E_(R) is fabricated by the following procedure.

First, a mold with a number of the balls 1 as cores is used and theresin connector 2 is molded by injection molding of 6•6nylon-polyamide-base elastomer (made by Toray Corporation, commercialname: Pebax® 5533SA, mold shrinkage rate: 0.43% in flow direction and0.74% in direction orthogonal to flow, Shore hardness: 55) andfabricated by removing it from the mold along with the number of balls1.

Next, the endless retainer E_(R) fabricated in this way is subjected toan oil absorbing treatment or a water absorbing treatment by thefollowing methods, length dimensions before and after the treatment aremeasured and dimension change rates before and after the oil absorbingor the water absorbing treatment are calculated.

Further, in calculating the dimension change rates before and after theoil absorbing or the water absorbing treatment, the dimension changerates are measured by preparing 5 pieces of samples of the endlessretainer E_(R) and in respect of each of the samples.

[Method A]

The molded endless retainer E_(R) is immediately dipped into amineral-base lubricant at normal temperature and left in the lubricantas it is and the dimension change rates (elongation rates) arecalculated by measuring the lengths of the samples of the endlessretainer E_(R) after 1 hour, after 6 hours, after 50 hours, after 80hours and after 124 hours since the dipping operation has been started.

Table 1 shows the lengths of the samples of the endless retainer E_(R)in starting dipping operation, 1 hour after start of dipping and 6 hoursafter start of dipping and the elongation rates at the respectivemeasurements are shown by FIG. 5.

                  TABLE 1                                                         ______________________________________                                        Length (mm, upper column) and                                                 Elongation rate (%, lower column)                                                                  1 hour after                                                                             6 hours after                                 Sample No.                                                                               Start of dipping                                                                         start of dipping                                                                         start of dipping                             ______________________________________                                        No. 1   115.988      116.144    116.552                                                            (0.00)                                                                                                            (0.49)               No. 2           115.973                                                                                                              116.656                                     (0.00)                                                                                                            (0.59)               No. 3            116.058                                                                                                             116.548                                     (0.00)                                                                                                            (0.42)               No. 4            116.017                                                                                                             116.636                                     (0.00)                                                                                                            (0.53)               No. 5            115.883                                                                                                             116.655                                     (0.00)                                                   ______________________________________                                                                        (0.67)                                    

The rotatability of ball is investigated as follows in respect of thesamples of the endless retainer E_(R). That is, the sample of theendless retainer E_(R) is sandwiched between two sheets of plates, oneof the plates is fixed while the other thereof is moved and whether thesample of the endless retainer E_(R) is moved at the occasion andsmoothness of movement when the sample is moved are qualitativelyinvestigated.

As a result, in respect of the samples of 1 hour after start of dipping,the rotatability of ball is confirmed except the sample of No. 3, thecomparatively smooth rotatability of ball is confirmed in respect of thesamples of 6 hours after start of dipping and the extremely excellentrotatability of ball is confirmed in respect of samples of 50 hoursafter start of dipping.

[Method B]

The molded samples of the endless retainer E_(R) are immediately dippedinto a mineral-base lubricant at normal temperature for 5 minutes,thereafter taken out from the lubricant and left in a room, and thedimension change rates (elongation rates) are calculated by measuringlengths of the samples of the endless retainer E_(R) at immediatelyafter taking them out from the lubricant (0 hour), 24 hours thereafter,45 hours thereafter, 69 hours thereafter, 118 hours thereafter and 190hours thereafter, respectively.

The result is shown by FIG. 6. Further, as a result of investigating therotatability of ball similar to the case of Method A mentioned above,the rotatability of ball is recognized in respect of the samples of theendless retainer E_(R) immediately after having been taken out from thelubricant except the sample of No. 2 and the comparatively excellentrotatability of ball is recognized in respect of the samples of 24 hoursor longer after starting to leave them in the room.

[Method C]

The molded samples of the endless retainer E_(R) are left in theatmosphere as they are (temperature 23° C., humidity 50 through 60%) andthe dimension change rates (elongation rates) are calculated bymeasuring lengths of the samples of the endless retainer E_(R) of 24hours after starting to leave them, 40 hours thereafter and 96 hoursthereafter, respectively. The result is shown in FIG. 7.

Further, as a result of investigating the rotatability of ball similarto the case of Method A mentioned above, the rotatability of ball isrecognized in respect of the samples of the endless retainer E_(R) of 24hours after starting to leave them in the atmosphere except the sampleof No. 1 and the rotatability of ball is recognized in respect of allthe samples of the endless retainer E_(R) of 48 hours after starting toleave them.

Embodiment 2

6•6 nylon-polyamide-base elastomer (made by Toray Corporation,commercial name: Pebax 5533SA) the same as that used in Embodiment 1mentioned above and polyester-base elastomer (made by Toray Corporationand DuPont Corporation, commercial name: Hytrel® 4767, mold shrinkagerate: 1.2 through 1.5%, hardness under JIS K7215: 47) are used, theresin connectors 2 are molded similar to Embodiment 1 mentioned above, aoil absorbing treatment is successively carried out in accordance withthe dipping method of Method A, the dimension change rate (elongationrate) in this occasion is time-sequentially investigated and a timeperiod (dimension stabilizing time) until the change in dimensions isstabilized within a range of the elongation rate of 0.5 through 1.5% incarrying out the oil absorbing treatment, is investigated. The result isshown by FIG. 8.

As is apparent from the result of FIG. 8, in the case of 6•6nylon-polyamide-base elastomer, the elongation rate exceeds about 0.8%at 100 minutes after starting to dip the sample in the oil absorbingtreatment, successively, rapid change in dimension is observed up toabout 200 hours and little by little change in dimension is causedthereafter even after 460 hours has elapsed. By contrast, in the case ofpolyester-base elastomer, the elongation rate exceeds 0.5% at about 50hours after staring to dip the sample in the oil absorbing treatment andreaches about 0.8% for 100 hours, a gradual change in dimension issuccessively observed up to about 200 hours, however, almost no changein dimension is observed thereafter even exceeding 500 hours.

As a result, it is known that by using polyester-base elastomer, a timeperiod for reaching a range of the preferable elongation rate of 0.5through 1.5% is prolonged compared with the case of 6•6nylon-polyamide-base elastomer, however, the dimension stabilizing timeperiod for stabilizing the change in dimension is significantlyshortened, which is advantageous in fabricating the endless retainerE_(R).

Application Example 1

A linear guide device for infinite sliding shown by FIG. 9 and FIG. 10is constituted by using the endless retainer E_(R) which has beensubjected to the oil absorbing or the water absorbing treatment inaccordance with Method B in Embodiment 1.

The linear guide device for infinite sliding is basically constituted bya rigid track rail (one bearing race) 4 made of metal, a rigid slidingbase (other bearing race) 5 made of metal, a ball guide member 6 made ofsynthetic resin and attached to the sliding base 5 by insert molding andlids 7 made of synthetic resin and attached to the sliding base 5 alongwith the ball guide member 6.

Further, the track rail 4 is formed with rolling faces 4a of balls 1 atboth shoulder portions thereof and the sliding base 5 is formed withloaded ball rolling faces 5a of the balls 1 on which load is applied andthrough holes 5b through which the balls 1 in an unloaded state pass.Further, the ball guide member 6 is formed with unloaded ball guideholes 6a for guiding rolling of the balls 1 under the unloaded state,loaded ball guide grooves 6b for guiding rolling of the balls 1 under aloaded state and direction change guiding units 6c for guiding to changethe direction of the balls 1 by communicating and connecting theunloaded ball holes 6a with the loaded ball guide grooves 6b by apredetermined radius of curvature. Further, the lid 7 is formed withdirection change guide grooves 7a for constituting direction changepaths 8 of the balls 1 along with the direction change guide portions 6cof the ball guide members 6 mentioned above.

According to the embodiment, an infinite track of the ball 1 isconstituted by the loaded ball rolling face 5a of the sliding base 5 aswell as the loaded ball guide groove 6b of the ball guide member 6opposed thereto, the unloaded ball guide hole 6a of the ball guidemember 6, the direction change guide portions 6c of the ball guidemembers 6 and the direction change guide grooves 7a of the lids 7opposed thereto.

In respect of the linear guide device fabricated in this way, rollingresistance of the sliding base 5 with respect to the track rail 4 ismeasured by fixing the track rail 4 and pushing the sliding base 5 by aload cell at a sampling frequency of 500 Hz of the load cell.

The result is as shown by FIG. 11 in which values of the rollingresistance in a moving region partitioned by bold lines are 1.389 Newton(N) in starting, 1.439 N as maximum rolling resistance, 1.179 N asminimum rolling resistance and 1.302 N as average rolling resistancewhich is found to be extremely smooth.

Industrial Applicability

An endless retainer according to the present invention is not onlyprovided with advantages where fabrication thereof is extremelyfacilitated, handling thereof is extremely easy without detachment ofrolling bodies and automation in integrating the retainer to a guidedevice can be carried out but is capable of providing extremely smoothrotatability to the rolling bodies with certainty.

Accordingly, the endless retainer of the present invention is extremelyuseful for use of, for example, a linear guide device or a curved guidedevice for infinite sliding and a guide device of pivoting bearing orthe like.

What is claimed is:
 1. An endless retainer of a guide device, said endless retainer comprising:a number of rolling bodies arranged at predetermined intervals for rolling at an inside of an infinite track formed in the guide device; a flexible resin connector having interposing portions interposed among the respective rolling bodies and connecting portions for connecting the respective interposing portions for holding the number of rolling bodies in an aligned state and rotatably; and wherein the resin connector is molded by an injection molding with the rolling bodies as cores by using a resin having a dimension change rate before and after an oil absorbing or a water absorbing treatment larger than a mold shrinkage rate and is provided with clearances between the resin connector and the rolling bodies formed by the oil absorbing or the water absorbing treatment.
 2. The endless retainer of a guide device according to claim 1:wherein a difference between the dimension change rate before and after the oil absorbing or the water absorbing treatment of the resin forming the resin connector falls in a range of 0.1 through 2.0%.
 3. The endless retainer of a guide device according to claim 1 or 2:wherein an oil used in the oil absorbing treatment is a mineral oil-base or a synthetic oil-base lubricant.
 4. The endless retainer of a guide device according to any one of claim 1 or 2:wherein chamfered guide portions for guiding a front end portion of the resin connector are installed at both distal ends of the resin connector.
 5. The endless retainer of a guide device according to any one of claim 1 or 2:wherein Shore hardness of the resin forming the resin connector falls in a range of 35 through
 75. 6. The endless retainer of a guide device according to any one of claim 1 or 2:wherein the resin forming the resin connector is any of polyamide-base elastomer, polyester-base elastomer, polyurethane-base elastomer, styrene-base elastomer and olefin-base elastomer.
 7. The endless retainer of a guide device according to any one of claim 1 or 2:wherein the rolling body is a ball.
 8. A method of fabricating an endless retainer of a guide device, said endless retainer comprising:a number of rolling bodies arranged at predetermined intervals for rolling at an inside of an infinite track formed in the guide device; a flexible resin connector having interposing portions interposed among the respective rolling bodies and connecting portions for connecting the respective interposing portions for holding the number of rolling bodies in an aligned state and rotatably, said method of fabricating the endless retainer comprising the steps of: molding the resin connector holding the number of rolling bodies by an injection molding with the number of rolling bodies as cores by using a resin having a dimension change rate before and after an oil absorbing or a water absorbing treatment larger than a mold shrinkage rate; and forming clearances between the resin connector and the respective rolling bodies for rotating the rolling bodies by subjecting the resin connector to the oil absorbing or the water absorbing treatment after having been removed from a mold.
 9. The method of fabricating an endless retainer according to claim 8:wherein the oil absorbing or the water absorbing treatment is carried out by dipping the resin connector holding the rolling bodies into an oil or water.
 10. The method of fabricating an endless retainer according to claim 8 or 9:wherein the oil used in the oil absorbing treatment is a mineral oil-base or a synthetic oil-base lubricant.
 11. The method of fabricating an endless retainer according to claim 8:wherein the resin forming the resin connector is any of polyamide-base elastomer, polyester-base elastomer, polyurethane-base elastomer, styrene-base elastomer and olefin-base elastomer.
 12. A guide device comprising:a pair of bearing races; a number of rolling bodies rolling at an inside of an infinite track formed between the pair of bearing races; wherein the number of rolling bodies are formed in an endless retainer in a chain-like shape by being held in an aligned state and rotatably by a flexible resin connector having interposing portions interposed among the respective rolling bodies and connecting portions for connecting the respective interposing portions; and wherein the resin connector is molded by an injection molding with the rolling bodies as cores by using a resin having a dimension change rate before and after an oil absorbing or a water absorbing treatment larger than a mold shrinkage rate and is provided with clearances between the resin connector and the rolling bodies formed by the oil absorbing or the water absorbing treatment. 